kotlinx-coroutines-reactive
使org.reactivestreams.Publisher
有awaitXXX
方法:
val person = peopleReactiveRepository.findById(personId).awaitSingle()
如果通过人员 ID 找不到人员,则此调用将抛出 NoSuchElementException 并且无法在用户代码中直接处理此异常。而 Spring MVCExceptionHandler
无法将此异常转换为用户友好的响应。
java.util.NoSuchElementException: No value received via onNext for awaitSingle
at kotlinx.coroutines.experimental.reactive.AwaitKt$awaitOne$$inlined$suspendCancellableCoroutine$lambda$1.onComplete(Await.kt:131) ~[kotlinx-coroutines-reactive-0.22.1.jar:na]
at reactor.core.publisher.StrictSubscriber.onComplete(StrictSubscriber.java:123) ~[reactor-core-3.1.2.RELEASE.jar:3.1.2.RELEASE]
at reactor.core.publisher.Operators$MultiSubscriptionSubscriber.onComplete(Operators.java:1327) ~[reactor-core-3.1.2.RELEASE.jar:3.1.2.RELEASE]
at reactor.core.publisher.FluxHide$SuppressFuseableSubscriber.onComplete(FluxHide.java:137) ~[reactor-core-3.1.2.RELEASE.jar:3.1.2.RELEASE]
at reactor.core.publisher.FluxMap$MapSubscriber.onComplete(FluxMap.java:130) ~[reactor-core-3.1.2.RELEASE.jar:3.1.2.RELEASE]
at reactor.core.publisher.MonoNext$NextSubscriber.onComplete(MonoNext.java:96) ~[reactor-core-3.1.2.RELEASE.jar:3.1.2.RELEASE]
at com.mongodb.reactivestreams.client.internal.ObservableToPublisher$1.onComplete(ObservableToPublisher.java:78) ~[mongodb-driver-reactivestreams-1.6.0.jar:na]
我能想到的一种方法如下:
val person = peopleRepository.findById(personId).awaitFirstOrDefault(null)
if (person == null) {
// do something
}
但我不认为这是一种优雅的方式。例如,可以提供一个名为awaitSingleOptional
.
有没有更好的 Kotlin 方法来处理这种情况?